The present invention relates generally to cytokine receptor proteins, and more specifically, to soluble truncated interleukin-1 receptor proteins.
Interleukin-1.alpha. and interleukin-1.beta. (IL-1.alpha. and IL-1 1.beta.) are distantly related polypeptide hormones which play a central role in the regulation of immune and inflammatory responses. These two proteins were originally both classified as IL-1, based on a shared lymphocyte activation factor (LAF) activity, and a common major cellular source, activated macrophages. As information has accumulated from studies using purified natural and recombinant IL-1 molecules, it has become clear that IL-1.alpha. and IL-1.beta. each mediate most, if not all, of the wide range of activities previously ascribed to IL-1.
IL-1.alpha. and IL-1.beta. mediate their biological activities via at least two classes of plasma membrane bound receptors. One of these classes of receptor is expressed primarily on T cells and fibroblasts. IL-1.alpha. and IL-1.beta. bind to this class of IL-1 receptor, resulting in transduction of a biological signal to various immune effector cells. Because mature full-length IL-1 receptors are bound to the plasma membrane, however, they cannot be effectively used in assay, diagnosis or therapy to regulate immune or inflammatory activities.